- Email: [email protected]
Synthesis of fly ash based zeolite-reduced graphene oxide composite and its evaluation as an adsorbent for arsenic removal
Accepted Manuscript Synthesis of Fly ash based zeolite-reduced graphene oxide composite and its evaluation as an adsorbent for arsenic removal
Richa Soni, Dericks Praise Shukla PII:
S0045-6535(18)32310-5
DOI:
10.1016/j.chemosphere.2018.11.203
Reference:
CHEM 22687
To appear in:
Chemosphere
Received Date:
19 March 2018
Accepted Date:
28 November 2018
Please cite this article as: Richa Soni, Dericks Praise Shukla, Synthesis of Fly ash based zeolitereduced graphene oxide composite and its evaluation as an adsorbent for arsenic removal, Chemosphere (2018), doi: 10.1016/j.chemosphere.2018.11.203
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1
Synthesis of Fly ash based zeolite-reduced graphene oxide composite and its evaluation
2
as an adsorbent for arsenic removal
3
Richa Sonia* and Dericks Praise Shuklaa
4
a
School of Engineering, Indian Institute of Technology, Mandi, 175005, Himachal Pradesh, India
5
Email: [email protected], [email protected]
6
Abstract: A zeolite-reduced graphene oxide (ZrGO) based composite was synthesized to
7
remove arsenic from water. To make a low-cost adsorbent, zeolite was synthesized using an
8
inexpensive waste material; fly ash, which was further used to produce the ZrGO composite.
9
Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and
10
Raman spectra were used to characterize the morphology and surface composition of the
11
synthesized materials. Synthesized materials: zeolite, rGO and ZrGO were evaluated as an
12
adsorbent to remove arsenic from water. The results indicated that all three were able to adsorb
13
arsenic from water but the removal efficiency of ZrGO was the best as it was able to bring
14
down the arsenic concentration within the WHO permissible limits. The maximum adsorption
15
capacity for 100 µg/L of initial arsenic concentration was found to be 49.23 µg/g. Results
16
indicate that pseudo second order kinetics describes the arsenic adsorption on ZrGO.
17
Adsorption isotherm study for ZrGO shows best fit for Redlich-Peterson model of adsorption.
18
Keywords: arsenic, fly ash, reduced graphene oxide, zeolite
19
1. Introduction
20
Arsenic, being one of the toxic pollutants is introduced in the environment through
21
weathering of rocks, discharge of industrial waste, use of fertilizers and pesticides, smelting of
22
metal ores, burning of fossil fuels (Altundoğan et al., 2000; Benner, 2010; Shukla et al., 2010;
23
Nidheesh and Singh, 2017). Arsenic is present in several forms in food and environmental
24
media but it is mainly encountered in drinking water as inorganic arsenic. In this form it is 1
ACCEPTED MANUSCRIPT 25
highly toxic and readily bioavailable (Camacho et al., 2011; Dubey et al., 2012). There are two
26
inorganic states of arsenic in natural water viz. Arsenite (As-III) and Arsenate (As-V). Short-
27
term exposure to high levels of arsenic is fatal, and long-term exposure to trace levels of arsenic
28
(i.e., inhalation, ingestion) may lead to several chronic diseases, including skin, cardiovascular,
29
respiratory diseases and cancer (Baskan and Pala, 2011; Polowczyk et al., 2016; Wu et al.,
30
2017). Therefore many countries and organizations including World Health Organization
31
(WHO) adopts the guideline of 10 µg/L as maximum permissible limit (Mohan and Pittman,
32
2007; Mondal et al., 2013).
33
In order to safeguard the environment and health problems caused by arsenic in water,
34
various treatment techniques which include coagulation, adsorption, ion exchange,
35
electrochemical process, membrane separation and reverse osmosis have been used for arsenic
36
removal (Kumar et al., 2004; Shevade and Ford, 2004; Kabir and Chowdhury, 2017). Among
37
the mentioned techniques, adsorption is a popular method owing to its advantage of ease of
38
operation, versatility, availability of various adsorbents and potential of regeneration
39
(Simeonidis et al., 2016; Li et al., 2018). Also economic feasibility and simple synthesis adds
40
up to the advantage of using adsorbents for removal (Baskan and Pala, 2011).
41
Till date, various adsorbents have been used for the removal of arsenic from water. In
42
recent past, zeolites have been explored as adsorbents due to their structural characteristics and
43
valuable properties in heavy metal removal from water (Chunfeng et al., 2009; Merrikhpour
44
and Jalali, 2013). Zeolites are three dimensional micro and mesoporous crystalline solids with
45
well-defined structures that contain aluminum, silicon and oxygen in their regular framework
46
(Tavolaro and Drioli, 1999; Wdowin et al., 2014). In addition, it should be noted that zeolites
47
are compatible with the environment; they are stable at high temperatures, in acidic and
48
corrosive environments, and also have potential selectivity towards some cations (Khatamian
49
et al., 2015). To reduce the cost of zeolite production, efforts have been made to find a material,
2
ACCEPTED MANUSCRIPT 50
which has abundant natural availability or is a waste material or an industrial by-product. Fly
51
ash (inexpensive waste material) based zeolites have been employed for heavy metal removal
52
by various researchers (Querol et al., 2006; Chunfeng et al., 2009; Polowczyk et al., 2016). In
53
the present study fly ash is used as a substrate for zeolite synthesis. Valorization of fly ash to
54
form zeolites is of great interest as zeolites have widespread industrial application and their
55
sale can make up for disposal cost as well as it will reduce the environmental liability
56
(Chunfeng et al., 2009; Musyoka et al., 2013).
57
Recently, graphene based materials have gained tremendous popularity for
58
environmental remediation and energy applications because of their high surface area and
59
functional groups (Wang et al., 2013a; Wang et al., 2013b; Yusuf et al., 2015). But, owing to
60
high cost, large scale and high quality synthesis, the applicability of graphene for commercial
61
scale applications is limited (Khatamian et al., 2015). In this regard, synthesis of graphene
62
oxide (GO) through chemical methods and its subsequent reduction to form reduced graphene
63
oxide (rGO) enhanced the possibility for the application of graphene derivatives as adsorbents
64
in water purification. The insulating/non-conducting characteristics of GO owing to the various
65
hydrophilic oxygen groups (epoxide, hydroxyl, carbonyl, and carboxyl groups) restricts its use
66
for various applications including water treatment (Zhu et al., 2014). Conversely, the tuneable
67
conductivity (Soni et al., 2018) (based on the degree of reduction) of rGO may be more suitable
68
for water treatment. On the other hand, graphene-based composites are emerging as a new class
69
of materials that promises applications in several fields (Luo et al., 2011). It is believed that
70
these composites exhibit modified properties compared with their individual components. It
71
may be proposed that zeolites can be considered as proper candidate for preparation of
72
graphene-based composites due to their valuable properties (Khatamian et al., 2015).
73
In present work, we proposed to prepare a zeolite-reduced graphene oxide (ZrGO)
74
based composite using a facile, cost effective process thereby integrating the advantageous
3
ACCEPTED MANUSCRIPT 75
features of individual adsorbents to evaluate the removal of arsenic (III) from water. As Arsenic
76
(III) is the most toxic and mobile form of Arsenic in the environment (Wu et al., 2017), hence,
77
the present study focusses on removal of Arsenic (III) from water. Zeolite was synthesized
78
using fly ash, thus making the process cost effective and environment friendly. The
79
performance evaluation of the synthesized composite, ZrGO was done and compared with
80
zeolite and rGO for arsenic removal from water. The obtained ZrGO composite shows better
81
adsorption towards arsenic as compared to their individual counterparts. Furthermore, the
82
adsorption kinetics and isotherms were studied for ZrGO to understand the adsorption
83
mechanism.
84
2. Materials and Methods
85
2.1 Chemicals and Materials
86
Graphite (99.99% pure), potassium permanganate (KMnO4), sodium nitrate (NaNO3),
87
hydrochloric acid (HCl), sodium hydroxide (NaOH) and hydrogen peroxide (H2O2) were
88
obtained from Merck. Sulphuric acid (H2SO4), arsenic trioxide (As2O3), sodium hydroxide
89
(NaOH) and hydrochloric acid (HCl) was obtained from Fisher Scientific. N-Methyl-2-
90
pyrrolidone (NMP) from Alfa Aesar. De-ionized (DI) water with a resistivity of 18.2 MΩ.cm
91
(from Elga Labwater) was used for cleaning and solution preparation.
92
2.2 Synthesis of zeolite using fly ash
93
Fly ash was collected from coal based power plant in India (NTPC, Shaktinagar unit). The
94
composition of as collected fly ash was determined using X-ray fluorescence (XRF) (Shimadzu
95
XRF 72 instrument) and has been tabulated in Table 1. Fly ash was heated at 300 °C for 6 h to
96
remove any volatile impurities. The fly ash samples were further washed with dilute HCl to
97
enhance the zeolitic activity (Ojha et al., 2004). Further the treated fly ash was mixed with
98
sodium hydroxide in a predetermined ratio (3:2). The mixture was grounded with the help of
4
ACCEPTED MANUSCRIPT 99
mortar and pestle and was heated again at 300 °C for 1 h. After an hour the mixture was cooled
100
and grounded again to ensure proper mixing. DI water was added to the grounded mixture (10
101
mL/g of mixture). The formed slurry was agitated in a glass beaker for 3 hours, after which it
102
was kept undisturbed at 90 °C for 6 h. The resultant precipitate was repeatedly washed with DI
103
water to remove any excess NaOH, after which it was filtered and dried.
104
Table 1: XRF analysis of the collected fly ash Oxide Mass (%) SiO2 61.28 Al2O3 30.17 Fe2O3 3.72 TiO2 1.52 K2O 1.13 SO3 1.57 CaO 0.55 MnO 0.05 ZnO 0.01
105 106
2.3 Synthesis of GO and rGO
107
GO was prepared using the modified Hummers method (Soni et al., 2016). Graphite flakes (1
108
g) along with conc. H2SO4 (50 mL) was poured into the beaker, kept in an ice bath and stirred
109
at 500 rpm for 30 min. Afterwards, a dark grey colour solution forms, to which NaNO3 (1 g)
110
was added. Solution was further stirred at 800 rpm for 90 min and KMnO4 (8 g) was slowly
111
added while stirring. Ice bath was removed and the stirring was continued for further 90 min.
112
The solution was further diluted by adding DI water (100 mL) with constant stirring for another
113
90 min. After this, the temperature was raised up to 95 °C and the solution was stirred for 30
114
min, which resulted in the colour change from dark grey to brown. The solution temperature
115
was decreased to 25 °C and was stirred overnight at 800 rpm. For reaction termination, the
116
brown colour solution is finally treated with 100 mL DI water and 3 mL H2O2 (30%), followed
117
by centrifugation and repeated washing with DI water (until pH ~7). The final yellow
118
dispersion was dried in a hot oven at 50 °C to get GO powder. 5
ACCEPTED MANUSCRIPT 119
To form rGO, 100 mL DI was added to100 mg GO powder. 25 mL NMP was added to the
120
slurry and was kept under UV exposure (λ = 254 nm) for 60 min. The final black dispersion
121
obtained was dried in a hot oven at 50 °C to get black rGO powder.
122
2.4 Synthesis of ZrGO composite
123
Equal amount of zeolite and GO are mixed and DI water was added to the mixture. The pale
124
yellow coloured slurry was kept under stirring for 3 d. After 3 d, NMP was added to the slurry
125
and was kept under UV exposure (λ = 254 nm) for an hour, resulting into a dark greyish rGO-
126
zeolite solution. The dipolar aprotic characteristics of NMP assists GO reduction under UV
127
exposure. The aqueous solution obtained above is dried at 100 °C in vacuum oven to result in
128
ZrGO powder. A schematic depicting the synthesis process of ZrGO is shown in Fig 1.
129 130 131
Fig 1: Schematic diagram for the synthesis of ZrGO. 2.5 Instruments and analytical conditions
132
The Fourier transform infrared (FTIR) spectra were recorded on dried powder using an Agilent
133
Technologies Cary 600 Series FTIR Spectrometer. The morphology and composition of
134
samples were examined using scanning electron microscopy- energy dispersive x-ray (SEM-
135
EDAX) on Nova Nano-SEM-450 instrument. Raman spectroscopy was performed on a
136
LabRAMHR Evolution confocal Raman spectrometer (Horiba, Japan) using green (532 nm)
137
laser excitation in the range (800–2000 cm−1). For Raman measurements, the aqueous solutions
138
were sonicated and drop-casted on cleaned p-Si wafers. Arsenic measurements were done by 6
ACCEPTED MANUSCRIPT 139
both portable Metalyser HM-1000 and ICP-MS (Thermo Scientific X series2). Deep UV light
140
(G64HO75, 130 w, 254 nm) from Arklite (measured from UVC Light Meter 850010, SPER
141
Scientific make), was used as a source for the reduction of GO.
142
2.6 Arsenic removal experiments
143
Arsenite stock solution (1000 µg/L) was prepared by dissolving arsenic trioxide in hydrochloric
144
acid and DI. Arsenic working solutions were freshly made by diluting the stock arsenic solution
145
until desired concentration using DI water. The adsorbent was added to 50 mL of working
146
arsenic solution and stirred at 600 rpm for a fixed time. After the treatment, the samples were
147
collected from the beaker, filtered using 0.45 µm nylon membrane filter and analysed for
148
residual arsenic solution. All the experiments were performed in duplicate to evaluate test
149
reproducibility under identical conditions and the arithmetic average result of the two
150
experiments is reported in this study. In the present study pH and adsorbent dose was fixed by
151
performing preliminary investigations on zeolite. Thereafter, a comparative evaluation of
152
arsenic removal was performed for synthesized zeolite, rGO and ZrGO.
153
3. Results and Discussions
154
3.1 Material Characterization
155
The synthesized materials are characterized using FTIR, RAMAN and SEM-EDAX. The
156
results are discussed below.
157
3.1.1
FTIR
158
The FTIR spectra for zeolite, GO, rGO and ZrGO is shown in Fig 2. Zeolite: The FTIR spectra
159
of zeolite is shown in Fig 2a. The IR peak at 1097 cm-1 and 1013.6 cm-1 is assigned to Si(Al)O4/2
160
tetrahedra. The peak at 771.3 cm-1 corresponds to the symmetric stretching vibration of SiO4
161
groups. The peak at 551.6 cm-1 are present either due to (Si/Al)O4 bending or the motion of the
162
external linkage of the AlO4 and SiO4 tetrahedra. The results corroborates with work of Ojha 7
ACCEPTED MANUSCRIPT 163
et al.(Ojha et al., 2004). GO: As demonstrated by the FTIR absorption spectrum (Fig 2b), the
164
characteristic sp3 hybridised carbon peak for GO is at 1602.6 cm-1. Additionally, the FTIR for
165
GO sheet also shows the presence of absorption band peaks for hydroxyl, carbonyl, ether and
166
carboxyl groups at 3360.6, 1715.2, 1398 & 1251.9 and 1026.8 & 946.1 cm−1, respectively.
167
rGO: On the other hand, for rGO, the FTIR absorption spectrum (Fig 2c) shows a characteristic
168
sp2 hybridised carbon peak for at 1655.6 cm-1. Moreover, a significant decrease in the intensity
169
of absorption bands peaks corresponding to oxygen functional groups (at 3252.7 cm-1 due to –
170
OH stretching 1395.6 cm-1 due to C–O stretching, and 1034.8 cm−1 due to C–O stretching)
171
confirming the photo-catalytic reduction of GO using NMP. Thus, after the reduction to rGO,
172
the functional groups containing oxygen are removed. The results for FTIR spectra of GO and
173
rGO are in line with Mahesh et al. (Mahesh et al., 2017) ZrGO: The FTIR spectra of ZrGO
174
(Fig 2d) shows a peak at 1038.8 cm-1 which corresponds to Si(Al)O4/2 tetrahedra. The peak at
175
1376.3 cm-1 and 1637.1 cm-1 corresponds to C–O stretching and sp2 hybridised carbon peak
176
respectively. Thus, ZrGO shows characteristic peaks of both zeolite and rGO.
177 178
Fig 2: FTIR absorption spectra for (a) zeolite (b) GO (c) rGO (d) ZrGO. 8
ACCEPTED MANUSCRIPT 179
3.1.2
RAMAN
180
To understand the evolution of rGO, ZrGO from GO, Raman studies have been carried out for
181
GO, rGO and ZrGO. Raman spectra, in Fig 3, show two peaks around 1345 and 1590 cm−1,
182
corresponding to first order D and G bands, respectively. The G band peak corresponds to E2g
183
symmetry of sp2 hybridised carbon atoms, while the D band corresponds to the breathing mode
184
of sp2 hybridised carbon atoms in the hexagonal ring along with the local defects and disorder
185
(Mahesh et al., 2017). The intensity ratio of the D and G bands (ID/IG) is an important and major
186
factor to distinguish GO, rGO and ZrGO composite for structural defects/disorders (Sun et al.,
187
2013). The enhancement of (ID/IG) from ~ 0.99 (GO) to 1.16 (rGO) confirms the reduction of
188
GO (Mahesh et al., 2017) and further enhancement of (ID/IG) to 1.26 confirms the formation
189
of ZrGO as addition of zeolite increases the defects in rGO structure.
190
Fig 3: RAMAN spectra of GO, rGO and ZrGO.
191 192
3.1.3
SEM-EDAX
193
To understand the morphology and elemental composition SEM-EDAX of Zeolite, GO, rGO
194
and ZrGO was performed. Zeolite: Irregular crystals in the SEM micrograph (Fig 4a) indicate
195
towards the formation of zeolite (Musyoka et al., 2013). Zeolites are basically aluminosilicates
196
and it is indicated by the presence of Si and Al content in EDAX (Fig 4b). Other elements 9
ACCEPTED MANUSCRIPT 197
present in the fly ash are sodium, magnesium, calcium, potassium and iron. GO: Morphology
198
of GO is observed as flaky texture reflecting its layered microstructure as shown in SEM image
199
(Fig 4c). Elemental composition (Fig 4d) also supports the formation of GO as it shows
200
presence of carbon and oxygen. rGO: The morphology of rGO (Fig 4e) is observed as layered
201
structure in form of multiple stacked sheets. It can be differentiated from GO by its elemental
202
composition (Fig 4f), nitrogen content in the EDAX is due to the reducing agent (NMP). Also,
203
the reduction of GO is evident by decrease in oxygen percentage. ZrGO: After GO was added,
204
the prepared ZrGO showed the structure of spherical particles (Fig 4g), which may be due to
205
the self-assembly between zeolite and rGO (Vander Waals and hydrogen bonding forces). SEM
206
images show that zeolite particles are decorated over rGO sheets and is indicative of successful
207
formation of the desired composite. Moreover, EDAX of ZrGO (Fig 4h) shows addition of
208
carbon, nitrogen and oxygen apart from the elements present in zeolite, thus indicating towards
209
successful formation of the composite.
10
ACCEPTED MANUSCRIPT
210 211
Fig 4: (a) SEM micrograph of zeolite and (b) elemental composition of zeolite (c) SEM
212
micrograph of GO (d) elemental composition of GO (e) SEM micrograph of rGO (f) elemental
213
composition of rGO (g) SEM micrograph of ZrGO and (b) elemental composition of ZrGO.
214
3.2 Preliminary investigations on synthesized zeolite
215
Preliminary investigations were carried out on prepared zeolite to fix the initial pH and
216
adsorbent dose for further experimentation and comparison purposes. The effect of pH on
217
arsenic adsorption by zeolite was investigated at acidic, neutral, and basic conditions. The pH 11
ACCEPTED MANUSCRIPT 218
of five 50 mL solutions of 100 µg/L arsenic was adjusted to values ranging from 2.0 to 10.0 by
219
adding 0.1MHCl or 0.1MNaOH. The solutions were then mixed with 100 mg of prepared
220
zeolite and stirred for 30 min. After 30 min, samples were removed from the beaker, filtered
221
(0.45 µm nylon membrane filter) and analysed for arsenic concentration. It can be clearly
222
observed (Fig 5a) that with the increase in basicity of the solution the residual arsenic decreases
223
and attains a minimum at pH 8. After which as the pH value is increased from 8 to 10, arsenic
224
concentration also increases slightly. This suggests that for the present study a pH value of 8 is
225
considered to be suitable. Several researchers like Suzuki et al. (Suzuki et al., 2000) and
226
Lenoble et al. (Lenoble et al., 2005) have also found that pH close to 8 has been found suitable
227
for arsenic (III) removal. As the pH increases, amount of negatively charged species of arsenic
228
increases and positively charged species decreases (Altundoğan et al., 2000) and for effective
229
treatment of arsenic (III), the pH of solution must be over 7.0 (Katsoyiannis and Zouboulis,
230
2002).
231 232
Fig 5 Effect of (a) pH (b) dose on residual arsenic concentration when zeolite is used as
233
adsorbent.
234
The effect of zeolite dosage on arsenic adsorption was investigated for five doses 25, 50,
235
75, 100, 125 and 150 mg. The experiments were conducted using 50 ml solution of 100 µg/L
236
arsenic at pH 8 for 30 min. Varying doses of prepared zeolite were mixed with arsenic solution
237
and stirred for 30 min. After 30 min, samples were removed from the beaker, filtered (0.45µm 12
ACCEPTED MANUSCRIPT 238
nylon membrane filter) and analysed for arsenic concentration. The results as obtained are
239
shown in Fig 5b which shows that with increase in zeolite dose the residual arsenic
240
concentration decreases upto the dose of 100 mg adsorbent after which the decrease in arsenic
241
is almost negligible. Therefore, for all the further experiments initial pH was fixed to 8 and
242
adsorbent dose was fixed to 100 µg/L.
243
3.3 Effect of initial arsenic concentration on zeolite, rGO and ZrGO
244
The effect of initial arsenic concentration was studied for zeolite, rGO and ZrGO. The
245
experiments were conducted at a fixed pH of 8 and fixed adsorbent dosage of 100 mg for a
246
duration of 90 min. The samples were collected in an interval of 15 min. It can be observed
247
that at a constant treatment time for all the adsorbents used, an increase in value of initial
248
arsenic concentration also increases value of the residual arsenic concentration. At lower
249
arsenic concentrations, most of the arsenic ions present in the solution would interact with the
250
binding sites facilitating higher adsorption. It can be observed from the Fig 6 that for 100 µg/L
251
initial arsenic concentration and 45 min of treatment time the residual arsenic concentration for
252
zeolite was 24.19 µg/L, for rGO was 19.56 µg/L, and for ZrGO was 8.23 µg/L. Thus, it shows
253
that ZrGO is a better adsorbent for arsenic removal (̴ 93% removal in 45 min) when compared
254
with zeolite and rGO. ZrGO was able to bring down the arsenic concentration well within the
255
WHO permissible limits (<10 µg/L). It can also be observed from the Fig 6a and 6c that at a
256
fixed time of 90 min the residual arsenic increases from 1.52 to 8.19 µg/L as the initial arsenic
257
concentration is increased from 100 to 300 µg/L. It is because at lower concentrations, most of
258
the arsenic ions present in solution would interact with the binding sites facilitating higher
259
adsorption (Chutia et al., 2009).
13
ACCEPTED MANUSCRIPT
260 261
Fig 6: Effect of varying initial arsenic concentration on residual arsenic concentration using
262
zeolite, rGO and ZrGO (a) initial arsenic = 300 µg/L (b) initial arsenic = 200 µg/L (c) initial
263
arsenic = 100 µg/L.
264
For further analysis of results, a graph (Fig 7) was also plotted for ZrGO between time
265
and adsorption capacity (q). It was observed that adsorption capacity increases from 49.24 μg/g
266
to 145.91 μg/g when initial arsenic concentration is increased from 100 to 300 μg/L. This
267
indicates that with the increase of the concentration of arsenic ions in solution, more ions are
268
readily available for adsorption hence increasing the adsorption performance. At higher
269
concentrations, some energetically less favourable sites become involved (Baskan and Pala,
270
2011). However, the sorption is reached to saturated point when the limited active surface sites
271
on the sorbents are covered fully by the sorbate. The present findings of adsorption capacity at
272
100 μg/L initial arsenic (III) concentration was 49.24 μg/g, which was found to be higher than
273
the
274
(Thirunavukkarasu et al., 2003), Iron oxide coated sand (28 µg/g) (Gupta et al., 2005), zeolite
275
(17 µg/g) (Elizalde-González et al., 2001), Oak bark char (7.4 µg/g) (Mohan et al., 2007).
previously
reported
adsorbents
like
granular
ferric
hydroxide
(47.5
µg/g)
276
The arsenic adsorption on zeolites is the result of exchange between terminal aluminol
277
or silanol hydroxyl groups and adsorbate anionic species. The adsorption mechanisms of
278
arsenic anions onto graphene-based materials are complex, the most dominant mechanisms
279
reported in the literature are physical adsorption, chemical interaction and electrostatic
280
attraction (Yang et al., 2017). The mechanism of As (III) adsorption on rGO based composites
14
ACCEPTED MANUSCRIPT 281
should be interpreted as surface complexation modeling. The surface complexation reaction
282
between As(III) and graphene based composites are proposed by Yang et al (Yang et al., 2017).
283
For further information on possible schematic illustration, see Sinha & Shukla (Data in brief;
284
submitted)
285
286 287
Fig 7: Arsenic adsorption by ZrGO as a function of time for varying initial arsenic
288
concentration.
289
4. Adsorption kinetics and adsorption isotherms
290
ZrGO gave the best result as an adsorbent in the present study and was able to bring down the
291
residual arsenic concentration well within the WHO standards. Therefore, the adsorption
292
kinetic and adsorption isotherm study was performed for the data obtained for ZrGO.
293
For the present study, the plots were made for three initial arsenic concentrations (100, 200,
294
300 µg/L). The experimental data was fitted in the mentioned three kinetic models. The average
295
R2 value for pseudo first order kinetic model is 0.976, for pseudo second order kinetic model
296
it is 0.999 and for intra-particle diffusion it is 0.893 The detailed results of adsorption kinetics
297
are presented in Sinha & Shukla (Data in brief; submitted). These results indicate that the
298
adsorption system belongs to the pseudo second-order kinetic model. Similar results have been 15
ACCEPTED MANUSCRIPT 299
obtained by Khatamian et al.(Khatamian et al., 2015). In this model, the rate-limiting step is
300
the surface adsorption that involves chemisorption, where the removal from a solution is due
301
to physicochemical interactions between the two phases (Wang et al., 2007). Liu et al. (Liu et
302
al., 2011) has also mentioned that pseudo-second order kinetic assumes that chemisorption
303
controls the adsorption rate.
304
The experimental data were fitted with Langmuir, Freundlich and Redlich–Peterson isotherms.
305
The R2 values of Redlich–Peterson is the best, 0.986. Thus, it can be concluded that adsorption
306
of arsenic to ZrGO is hybrid mechanism and does not follow ideal monolayer adsorption. For
307
further information on adsorption isotherm analysis see Sinha & Shukla (Data in brief;
308
submitted).
309
5. Conclusions
310
ZrGO composite was successfully synthesized by a simple cost-effective method and can be
311
used as an effective adsorbent for arsenic removal in aqueous solutions. Results showed that
312
ZrGO gave the best performance as an adsorbent to remove arsenic when compared with
313
zeolite and rGO individually. ZrGO shows 97% removal efficiency and was able to bring down
314
the arsenic concentration well within WHO limits. The kinetic model fits the pseudo first order
315
kinetics and indicates the adsorption mechanism to be chemisorption. Adsorption isotherm
316
suitably described by Redlich Peterson isotherm model indicates that the reaction between
317
ZrGO and arsenic in solution is a hybrid mechanism and not an ideal monolayer adsorption.
318
The effective performance of synthesized ZrGO in arsenic removal from water should be
319
amenable to potential water treatment applications in consideration of ZrGO’s low-cost, use of
320
waste material, and favourable adsorption process.
321
Acknowledgements
16
ACCEPTED MANUSCRIPT 322
This work was financially supported by Science and Engineering Board (SERB) project no.
323
PDF/2016/000338 and DST Fast track project no SR/FTP/ES-6/2013.
324
References
325
Altundoğan, H.S., Altundoğan, S., TuÈmen, F., Bildik, M., 2000. Arsenic removal from
326
aqueous solutions by adsorption on red mud. Waste Management 20, 761-767.
327
Baskan, M.B., Pala, A., 2011. Removal of arsenic from drinking water using modified natural
328
zeolite. Desalination 281, 396-403.
329
Benner, S., 2010. Hydrology: anthropogenic arsenic. Nature Geoscience 3, 5-6.
330
Camacho, L.M., Parra, R.R., Deng, S., 2011. Arsenic removal from groundwater by MnO 2-
331
modified natural clinoptilolite zeolite: effects of pH and initial feed concentration. Journal of
332
hazardous materials 189, 286-293.
333
Chunfeng, W., Jiansheng, L., Xia, S., Lianjun, W., Xiuyun, S., 2009. Evaluation of zeolites
334
synthesized from fly ash as potential adsorbents for wastewater containing heavy metals.
335
Journal of Environmental Sciences 21, 127-136.
336
Chutia, P., Kato, S., Kojima, T., Satokawa, S., 2009. Arsenic adsorption from aqueous solution
337
on synthetic zeolites. Journal of Hazardous Materials 162, 440-447.
338
Dubey, C.S., Mishra, B.K., Shukla, D.P., Singh, R.P., Tajbakhsh, M., Sakhare, P., 2012.
339
Anthropogenic arsenic menace in Delhi Yamuna flood plains. Environmental Earth Sciences
340
65, 131-139.
341
El Nemr, A., 2009. Potential of pomegranate husk carbon for Cr (VI) removal from wastewater:
342
Kinetic and isotherm studies. Journal of Hazardous Materials 161, 132-141.
343
Elizalde-González, M., Mattusch, J., Einicke, W.-D., Wennrich, R., 2001. Sorption on natural
344
solids for arsenic removal. Chemical Engineering Journal 81, 187-195.
345
Foo, K., Hameed, B., 2010. Insights into the modeling of adsorption isotherm systems.
346
Chemical Engineering Journal 156, 2-10. 17
ACCEPTED MANUSCRIPT 347
Gimbert, F., Morin-Crini, N., Renault, F., Badot, P.-M., Crini, G., 2008. Adsorption isotherm
348
models for dye removal by cationized starch-based material in a single component system:
349
error analysis. Journal of Hazardous Materials 157, 34-46.
350
Gupta, V., Saini, V., Jain, N., 2005. Adsorption of As (III) from aqueous solutions by iron
351
oxide-coated sand. Journal of colloid and interface science 288, 55-60.
352
Ho, Y., Porter, J., McKay, G., 2002. Equilibrium isotherm studies for the sorption of divalent
353
metal ions onto peat: copper, nickel and lead single component systems. Water, Air, and Soil
354
Pollution 141, 1-33.
355
Hossain, M., Ngo, H., Guo, W., 2013. Introductory of Microsoft Excel SOLVER function-
356
spreadsheet method for isotherm and kinetics modelling of metals biosorption in water and
357
wastewater. Journal of Water Sustainability.
358
Hossain, M., Ngo, H., Guo, W., Setiadi, T., 2012. Adsorption and desorption of copper (II)
359
ions onto garden grass. Bioresource technology 121, 386-395.
360
Kabir, F., Chowdhury, S., 2017. Arsenic removal methods for drinking water in the developing
361
countries: technological developments and research needs. Environmental Science and
362
Pollution Research 24, 24102-24120.
363
Katsoyiannis, I.A., Zouboulis, A.I., 2002. Removal of arsenic from contaminated water sources
364
by sorption onto iron-oxide-coated polymeric materials. Water research 36, 5141-5155.
365
Khatamian, M., Khodakarampoor, N., Oskoui, M.S., Kazemian, N., 2015. Synthesis and
366
characterization of RGO/zeolite composites for the removal of arsenic from contaminated
367
water. RSC Advances 5, 35352-35360.
368
Kumar, K.V., 2007. Optimum sorption isotherm by linear and non-linear methods for malachite
369
green onto lemon peel. Dyes and Pigments 74, 595-597.
370
Kumar, P.R., Chaudhari, S., Khilar, K.C., Mahajan, S., 2004. Removal of arsenic from water
371
by electrocoagulation. Chemosphere 55, 1245-1252.
18
ACCEPTED MANUSCRIPT 372
Langmuir, I., 1916. The constitution and fundamental properties of solids and liquids. Part I.
373
Solids. Journal of the American chemical society 38, 2221-2295.
374
Lenoble, V., Laclautre, C., Deluchat, V., Serpaud, B., Bollinger, J.-C., 2005. Arsenic removal
375
by adsorption on iron (III) phosphate. Journal of hazardous materials 123, 262-268.
376
Li, Z., Wang, L., Meng, J., Liu, X., Xu, J., Wang, F., Brookes, P., 2018. Zeolite-supported
377
nanoscale zero-valent iron: New findings on simultaneous adsorption of Cd (II), Pb (II), and
378
As (III) in aqueous solution and soil. Journal of hazardous materials 344, 1-11.
379
Liu, B., Wang, D., Gao, X., Zhang, L., Xu, Y., Li, Y., 2011. Removal of arsenic from Laminaria
380
japonica Aresch juice using As (III)-imprinted chitosan resin. European Food Research and
381
Technology 232, 911.
382
Luo, Y.-B., Cheng, J.-S., Ma, Q., Feng, Y.-Q., Li, J.-H., 2011. Graphene-polymer composite:
383
extraction of polycyclic aromatic hydrocarbons from water samples by stir rod sorptive
384
extraction. Analytical Methods 3, 92-98.
385
Mahesh, S., Pawan, K., Rudra, K., Satinder Kumar, S., Ajay, S., 2017. Photo-catalytic
386
reduction of oxygenated graphene dispersions for supercapacitor applications. Journal of
387
Physics D: Applied Physics 50, 124003.
388
Merrikhpour, H., Jalali, M., 2013. Comparative and competitive adsorption of cadmium,
389
copper, nickel, and lead ions by Iranian natural zeolite. Clean Technologies and Environmental
390
Policy 15, 303-316.
391
Mohan, D., Pittman, C.U., 2007. Arsenic removal from water/wastewater using adsorbents—
392
a critical review. Journal of Hazardous materials 142, 1-53.
393
Mohan, D., Pittman, C.U., Bricka, M., Smith, F., Yancey, B., Mohammad, J., Steele, P.H.,
394
Alexandre-Franco, M.F., Gómez-Serrano, V., Gong, H., 2007. Sorption of arsenic, cadmium,
395
and lead by chars produced from fast pyrolysis of wood and bark during bio-oil production.
396
Journal of colloid and interface science 310, 57-73.
19
ACCEPTED MANUSCRIPT 397
Mondal, P., Bhowmick, S., Chatterjee, D., Figoli, A., Van der Bruggen, B., 2013. Remediation
398
of inorganic arsenic in groundwater for safe water supply: a critical assessment of technological
399
solutions. Chemosphere 92, 157-170.
400
Musyoka, N.M., Petrik, L.F., Fatoba, O.O., Hums, E., 2013. Synthesis of zeolites from coal fly
401
ash using mine waters. Minerals Engineering 53, 9-15.
402
Ng, J., Cheung, W., McKay, G., 2002. Equilibrium studies of the sorption of Cu (II) ions onto
403
chitosan. Journal of Colloid and Interface Science 255, 64-74.
404
Nidheesh, P., Singh, T.A., 2017. Arsenic removal by electrocoagulation process: Recent trends
405
and removal mechanism. Chemosphere 181, 418-432.
406
Ojha, K., Pradhan, N.C., Samanta, A.N., 2004. Zeolite from fly ash: synthesis and
407
characterization. Bulletin of Materials Science 27, 555-564.
408
Polowczyk, I., Bastrzyk, A., Ulatowska, J., Szczałba, E., Koźlecki, T., Sadowski, Z., 2016.
409
Influence of pH on arsenic (III) removal by fly ash. Separation Science and Technology 51,
410
2612-2619.
411
Querol, X., Alastuey, A., Moreno, N., Alvarez-Ayuso, E., Garcı́a-Sánchez, A., Cama, J.,
412
Ayora, C., Simón, M., 2006. Immobilization of heavy metals in polluted soils by the addition
413
of zeolitic material synthesized from coal fly ash. Chemosphere 62, 171-180.
414
Redlich, O., Peterson, D.L., 1959. A useful adsorption isotherm. Journal of Physical Chemistry
415
63, 1024-1024.
416
Shevade, S., Ford, R.G., 2004. Use of synthetic zeolites for arsenate removal from pollutant
417
water. Water Research 38, 3197-3204.
418
Shukla, D.P., Dubey, C., Singh, N.P., Tajbakhsh, M., Chaudhry, M., 2010. Sources and
419
controls of Arsenic contamination in groundwater of Rajnandgaon and Kanker District,
420
Chattisgarh Central India. Journal of hydrology 395, 49-66.
20
ACCEPTED MANUSCRIPT 421
Simeonidis, K., Mourdikoudis, S., Kaprara, E., Mitrakas, M., Polavarapu, L., 2016. Inorganic
422
engineered nanoparticles in drinking water treatment: a critical review. Environmental Science:
423
Water Research & Technology 2, 43-70.
424
Sinha, R., Mathur, S., 2016. Control of aluminium in treated water after defluoridation by
425
electrocoagulation and modelling of adsorption isotherms. Desalination and Water Treatment
426
57, 13760-13769.
427
Soni, M., Arora, T., Khosla, R., Kumar, P., Soni, A., Sharma, S.K., 2016. Integration of Highly
428
Sensitive Oxygenated Graphene With Aluminum Micro-Interdigitated Electrode Array Based
429
Molecular Sensor for Detection of Aqueous Fluoride Anions. IEEE Sensors Journal 16, 1524-
430
1531.
431
Soni, M., Kumar, P., Pandey, J., Sharma, S.K., Soni, A., 2018. Scalable and site specific
432
functionalization of reduced graphene oxide for circuit elements and flexible electronics.
433
Carbon 128, 172-178.
434
Sun, H., Wang, Y., Liu, S., Ge, L., Wang, L., Zhu, Z., Wang, S., 2013. Facile synthesis of
435
nitrogen doped reduced graphene oxide as a superior metal-free catalyst for oxidation.
436
Chemical Communications 49, 9914-9916.
437
Suzuki, T.M., Bomani, J.O., Matsunaga, H., Yokoyama, T., 2000. Preparation of porous resin
438
loaded with crystalline hydrous zirconium oxide and its application to the removal of arsenic.
439
Reactive and functional Polymers 43, 165-172.
440
Tavolaro, A., Drioli, E., 1999. Zeolite membranes. Advanced materials 11, 975-996.
441
Thirunavukkarasu, O., Viraraghavan, T., Subramanian, K., 2003. Arsenic removal from
442
drinking water using granular ferric hydroxide. Water Sa 29, 161-170.
443
Vanderborght, B.M., Van Grieken, R.E., 1977. Enrichment of trace metals in water by
444
adsorption on activated carbon. Analytical chemistry 49, 311-316.
21
ACCEPTED MANUSCRIPT 445
Wang, H., Yuan, X., Wu, Y., Huang, H., Peng, X., Zeng, G., Zhong, H., Liang, J., Ren, M.,
446
2013a. Graphene-based materials: fabrication, characterization and application for the
447
decontamination of wastewater and wastegas and hydrogen storage/generation. Advances in
448
colloid and interface science 195, 19-40.
449
Wang, H., Zhou, A., Peng, F., Yu, H., Yang, J., 2007. Mechanism study on adsorption of
450
acidified multiwalled carbon nanotubes to Pb (II). Journal of Colloid and Interface Science
451
316, 277-283.
452
Wang, S., Sun, H., Ang, H.-M., Tadé, M., 2013b. Adsorptive remediation of environmental
453
pollutants using novel graphene-based nanomaterials. Chemical Engineering Journal 226, 336-
454
347.
455
Wdowin, M., Franus, M., Panek, R., Badura, L., Franus, W., 2014. The conversion technology
456
of fly ash into zeolites. Clean Technologies and Environmental Policy 16, 1217-1223.
457
Wu, L.-K., Wu, H., Liu, Z.-Z., Cao, H.-Z., Hou, G.-Y., Tang, Y.-P., Zheng, G.-Q., 2017. Highly
458
porous copper ferrite foam: A promising adsorbent for efficient removal of As (III) and As (V)
459
from water. Journal of Hazardous Materials.
460
Yang, X., Xia, L., Song, S., 2017. Arsenic adsorption from water using graphene-based
461
materials as adsorbents: a critical review. Surface Review and Letters 24, 1730001.
462
Yusuf, M., Elfghi, F., Zaidi, S.A., Abdullah, E., Khan, M.A., 2015. Applications of graphene
463
and its derivatives as an adsorbent for heavy metal and dye removal: a systematic and
464
comprehensive overview. RSC Advances 5, 50392-50420.
465
Zhu, J., Wang, Y., Liu, J., Zhang, Y., 2014. Facile one-pot synthesis of novel spherical zeolite–
466
reduced graphene oxide composites for cationic dye adsorption. Industrial & Engineering
467
Chemistry Research 53, 13711-13717.
468
22
ACCEPTED MANUSCRIPT Highlights
Fly ash based ZrGO was successfully synthesized by a simple and cost-effective process.
ZrGO was able to reduce the arsenic concentration within WHO permissible limit.
ZrGO shows 97% removal efficiency.
Adsorption capacity of ZrGO was 49.23-145.91 µg/g.
Richa Soni, Dericks Praise Shukla PII:
S0045-6535(18)32310-5
DOI:
10.1016/j.chemosphere.2018.11.203
Reference:
CHEM 22687
To appear in:
Chemosphere
Received Date:
19 March 2018
Accepted Date:
28 November 2018
Please cite this article as: Richa Soni, Dericks Praise Shukla, Synthesis of Fly ash based zeolitereduced graphene oxide composite and its evaluation as an adsorbent for arsenic removal, Chemosphere (2018), doi: 10.1016/j.chemosphere.2018.11.203
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1
Synthesis of Fly ash based zeolite-reduced graphene oxide composite and its evaluation
2
as an adsorbent for arsenic removal
3
Richa Sonia* and Dericks Praise Shuklaa
4
a
School of Engineering, Indian Institute of Technology, Mandi, 175005, Himachal Pradesh, India
5
Email: [email protected], [email protected]
6
Abstract: A zeolite-reduced graphene oxide (ZrGO) based composite was synthesized to
7
remove arsenic from water. To make a low-cost adsorbent, zeolite was synthesized using an
8
inexpensive waste material; fly ash, which was further used to produce the ZrGO composite.
9
Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and
10
Raman spectra were used to characterize the morphology and surface composition of the
11
synthesized materials. Synthesized materials: zeolite, rGO and ZrGO were evaluated as an
12
adsorbent to remove arsenic from water. The results indicated that all three were able to adsorb
13
arsenic from water but the removal efficiency of ZrGO was the best as it was able to bring
14
down the arsenic concentration within the WHO permissible limits. The maximum adsorption
15
capacity for 100 µg/L of initial arsenic concentration was found to be 49.23 µg/g. Results
16
indicate that pseudo second order kinetics describes the arsenic adsorption on ZrGO.
17
Adsorption isotherm study for ZrGO shows best fit for Redlich-Peterson model of adsorption.
18
Keywords: arsenic, fly ash, reduced graphene oxide, zeolite
19
1. Introduction
20
Arsenic, being one of the toxic pollutants is introduced in the environment through
21
weathering of rocks, discharge of industrial waste, use of fertilizers and pesticides, smelting of
22
metal ores, burning of fossil fuels (Altundoğan et al., 2000; Benner, 2010; Shukla et al., 2010;
23
Nidheesh and Singh, 2017). Arsenic is present in several forms in food and environmental
24
media but it is mainly encountered in drinking water as inorganic arsenic. In this form it is 1
ACCEPTED MANUSCRIPT 25
highly toxic and readily bioavailable (Camacho et al., 2011; Dubey et al., 2012). There are two
26
inorganic states of arsenic in natural water viz. Arsenite (As-III) and Arsenate (As-V). Short-
27
term exposure to high levels of arsenic is fatal, and long-term exposure to trace levels of arsenic
28
(i.e., inhalation, ingestion) may lead to several chronic diseases, including skin, cardiovascular,
29
respiratory diseases and cancer (Baskan and Pala, 2011; Polowczyk et al., 2016; Wu et al.,
30
2017). Therefore many countries and organizations including World Health Organization
31
(WHO) adopts the guideline of 10 µg/L as maximum permissible limit (Mohan and Pittman,
32
2007; Mondal et al., 2013).
33
In order to safeguard the environment and health problems caused by arsenic in water,
34
various treatment techniques which include coagulation, adsorption, ion exchange,
35
electrochemical process, membrane separation and reverse osmosis have been used for arsenic
36
removal (Kumar et al., 2004; Shevade and Ford, 2004; Kabir and Chowdhury, 2017). Among
37
the mentioned techniques, adsorption is a popular method owing to its advantage of ease of
38
operation, versatility, availability of various adsorbents and potential of regeneration
39
(Simeonidis et al., 2016; Li et al., 2018). Also economic feasibility and simple synthesis adds
40
up to the advantage of using adsorbents for removal (Baskan and Pala, 2011).
41
Till date, various adsorbents have been used for the removal of arsenic from water. In
42
recent past, zeolites have been explored as adsorbents due to their structural characteristics and
43
valuable properties in heavy metal removal from water (Chunfeng et al., 2009; Merrikhpour
44
and Jalali, 2013). Zeolites are three dimensional micro and mesoporous crystalline solids with
45
well-defined structures that contain aluminum, silicon and oxygen in their regular framework
46
(Tavolaro and Drioli, 1999; Wdowin et al., 2014). In addition, it should be noted that zeolites
47
are compatible with the environment; they are stable at high temperatures, in acidic and
48
corrosive environments, and also have potential selectivity towards some cations (Khatamian
49
et al., 2015). To reduce the cost of zeolite production, efforts have been made to find a material,
2
ACCEPTED MANUSCRIPT 50
which has abundant natural availability or is a waste material or an industrial by-product. Fly
51
ash (inexpensive waste material) based zeolites have been employed for heavy metal removal
52
by various researchers (Querol et al., 2006; Chunfeng et al., 2009; Polowczyk et al., 2016). In
53
the present study fly ash is used as a substrate for zeolite synthesis. Valorization of fly ash to
54
form zeolites is of great interest as zeolites have widespread industrial application and their
55
sale can make up for disposal cost as well as it will reduce the environmental liability
56
(Chunfeng et al., 2009; Musyoka et al., 2013).
57
Recently, graphene based materials have gained tremendous popularity for
58
environmental remediation and energy applications because of their high surface area and
59
functional groups (Wang et al., 2013a; Wang et al., 2013b; Yusuf et al., 2015). But, owing to
60
high cost, large scale and high quality synthesis, the applicability of graphene for commercial
61
scale applications is limited (Khatamian et al., 2015). In this regard, synthesis of graphene
62
oxide (GO) through chemical methods and its subsequent reduction to form reduced graphene
63
oxide (rGO) enhanced the possibility for the application of graphene derivatives as adsorbents
64
in water purification. The insulating/non-conducting characteristics of GO owing to the various
65
hydrophilic oxygen groups (epoxide, hydroxyl, carbonyl, and carboxyl groups) restricts its use
66
for various applications including water treatment (Zhu et al., 2014). Conversely, the tuneable
67
conductivity (Soni et al., 2018) (based on the degree of reduction) of rGO may be more suitable
68
for water treatment. On the other hand, graphene-based composites are emerging as a new class
69
of materials that promises applications in several fields (Luo et al., 2011). It is believed that
70
these composites exhibit modified properties compared with their individual components. It
71
may be proposed that zeolites can be considered as proper candidate for preparation of
72
graphene-based composites due to their valuable properties (Khatamian et al., 2015).
73
In present work, we proposed to prepare a zeolite-reduced graphene oxide (ZrGO)
74
based composite using a facile, cost effective process thereby integrating the advantageous
3
ACCEPTED MANUSCRIPT 75
features of individual adsorbents to evaluate the removal of arsenic (III) from water. As Arsenic
76
(III) is the most toxic and mobile form of Arsenic in the environment (Wu et al., 2017), hence,
77
the present study focusses on removal of Arsenic (III) from water. Zeolite was synthesized
78
using fly ash, thus making the process cost effective and environment friendly. The
79
performance evaluation of the synthesized composite, ZrGO was done and compared with
80
zeolite and rGO for arsenic removal from water. The obtained ZrGO composite shows better
81
adsorption towards arsenic as compared to their individual counterparts. Furthermore, the
82
adsorption kinetics and isotherms were studied for ZrGO to understand the adsorption
83
mechanism.
84
2. Materials and Methods
85
2.1 Chemicals and Materials
86
Graphite (99.99% pure), potassium permanganate (KMnO4), sodium nitrate (NaNO3),
87
hydrochloric acid (HCl), sodium hydroxide (NaOH) and hydrogen peroxide (H2O2) were
88
obtained from Merck. Sulphuric acid (H2SO4), arsenic trioxide (As2O3), sodium hydroxide
89
(NaOH) and hydrochloric acid (HCl) was obtained from Fisher Scientific. N-Methyl-2-
90
pyrrolidone (NMP) from Alfa Aesar. De-ionized (DI) water with a resistivity of 18.2 MΩ.cm
91
(from Elga Labwater) was used for cleaning and solution preparation.
92
2.2 Synthesis of zeolite using fly ash
93
Fly ash was collected from coal based power plant in India (NTPC, Shaktinagar unit). The
94
composition of as collected fly ash was determined using X-ray fluorescence (XRF) (Shimadzu
95
XRF 72 instrument) and has been tabulated in Table 1. Fly ash was heated at 300 °C for 6 h to
96
remove any volatile impurities. The fly ash samples were further washed with dilute HCl to
97
enhance the zeolitic activity (Ojha et al., 2004). Further the treated fly ash was mixed with
98
sodium hydroxide in a predetermined ratio (3:2). The mixture was grounded with the help of
4
ACCEPTED MANUSCRIPT 99
mortar and pestle and was heated again at 300 °C for 1 h. After an hour the mixture was cooled
100
and grounded again to ensure proper mixing. DI water was added to the grounded mixture (10
101
mL/g of mixture). The formed slurry was agitated in a glass beaker for 3 hours, after which it
102
was kept undisturbed at 90 °C for 6 h. The resultant precipitate was repeatedly washed with DI
103
water to remove any excess NaOH, after which it was filtered and dried.
104
Table 1: XRF analysis of the collected fly ash Oxide Mass (%) SiO2 61.28 Al2O3 30.17 Fe2O3 3.72 TiO2 1.52 K2O 1.13 SO3 1.57 CaO 0.55 MnO 0.05 ZnO 0.01
105 106
2.3 Synthesis of GO and rGO
107
GO was prepared using the modified Hummers method (Soni et al., 2016). Graphite flakes (1
108
g) along with conc. H2SO4 (50 mL) was poured into the beaker, kept in an ice bath and stirred
109
at 500 rpm for 30 min. Afterwards, a dark grey colour solution forms, to which NaNO3 (1 g)
110
was added. Solution was further stirred at 800 rpm for 90 min and KMnO4 (8 g) was slowly
111
added while stirring. Ice bath was removed and the stirring was continued for further 90 min.
112
The solution was further diluted by adding DI water (100 mL) with constant stirring for another
113
90 min. After this, the temperature was raised up to 95 °C and the solution was stirred for 30
114
min, which resulted in the colour change from dark grey to brown. The solution temperature
115
was decreased to 25 °C and was stirred overnight at 800 rpm. For reaction termination, the
116
brown colour solution is finally treated with 100 mL DI water and 3 mL H2O2 (30%), followed
117
by centrifugation and repeated washing with DI water (until pH ~7). The final yellow
118
dispersion was dried in a hot oven at 50 °C to get GO powder. 5
ACCEPTED MANUSCRIPT 119
To form rGO, 100 mL DI was added to100 mg GO powder. 25 mL NMP was added to the
120
slurry and was kept under UV exposure (λ = 254 nm) for 60 min. The final black dispersion
121
obtained was dried in a hot oven at 50 °C to get black rGO powder.
122
2.4 Synthesis of ZrGO composite
123
Equal amount of zeolite and GO are mixed and DI water was added to the mixture. The pale
124
yellow coloured slurry was kept under stirring for 3 d. After 3 d, NMP was added to the slurry
125
and was kept under UV exposure (λ = 254 nm) for an hour, resulting into a dark greyish rGO-
126
zeolite solution. The dipolar aprotic characteristics of NMP assists GO reduction under UV
127
exposure. The aqueous solution obtained above is dried at 100 °C in vacuum oven to result in
128
ZrGO powder. A schematic depicting the synthesis process of ZrGO is shown in Fig 1.
129 130 131
Fig 1: Schematic diagram for the synthesis of ZrGO. 2.5 Instruments and analytical conditions
132
The Fourier transform infrared (FTIR) spectra were recorded on dried powder using an Agilent
133
Technologies Cary 600 Series FTIR Spectrometer. The morphology and composition of
134
samples were examined using scanning electron microscopy- energy dispersive x-ray (SEM-
135
EDAX) on Nova Nano-SEM-450 instrument. Raman spectroscopy was performed on a
136
LabRAMHR Evolution confocal Raman spectrometer (Horiba, Japan) using green (532 nm)
137
laser excitation in the range (800–2000 cm−1). For Raman measurements, the aqueous solutions
138
were sonicated and drop-casted on cleaned p-Si wafers. Arsenic measurements were done by 6
ACCEPTED MANUSCRIPT 139
both portable Metalyser HM-1000 and ICP-MS (Thermo Scientific X series2). Deep UV light
140
(G64HO75, 130 w, 254 nm) from Arklite (measured from UVC Light Meter 850010, SPER
141
Scientific make), was used as a source for the reduction of GO.
142
2.6 Arsenic removal experiments
143
Arsenite stock solution (1000 µg/L) was prepared by dissolving arsenic trioxide in hydrochloric
144
acid and DI. Arsenic working solutions were freshly made by diluting the stock arsenic solution
145
until desired concentration using DI water. The adsorbent was added to 50 mL of working
146
arsenic solution and stirred at 600 rpm for a fixed time. After the treatment, the samples were
147
collected from the beaker, filtered using 0.45 µm nylon membrane filter and analysed for
148
residual arsenic solution. All the experiments were performed in duplicate to evaluate test
149
reproducibility under identical conditions and the arithmetic average result of the two
150
experiments is reported in this study. In the present study pH and adsorbent dose was fixed by
151
performing preliminary investigations on zeolite. Thereafter, a comparative evaluation of
152
arsenic removal was performed for synthesized zeolite, rGO and ZrGO.
153
3. Results and Discussions
154
3.1 Material Characterization
155
The synthesized materials are characterized using FTIR, RAMAN and SEM-EDAX. The
156
results are discussed below.
157
3.1.1
FTIR
158
The FTIR spectra for zeolite, GO, rGO and ZrGO is shown in Fig 2. Zeolite: The FTIR spectra
159
of zeolite is shown in Fig 2a. The IR peak at 1097 cm-1 and 1013.6 cm-1 is assigned to Si(Al)O4/2
160
tetrahedra. The peak at 771.3 cm-1 corresponds to the symmetric stretching vibration of SiO4
161
groups. The peak at 551.6 cm-1 are present either due to (Si/Al)O4 bending or the motion of the
162
external linkage of the AlO4 and SiO4 tetrahedra. The results corroborates with work of Ojha 7
ACCEPTED MANUSCRIPT 163
et al.(Ojha et al., 2004). GO: As demonstrated by the FTIR absorption spectrum (Fig 2b), the
164
characteristic sp3 hybridised carbon peak for GO is at 1602.6 cm-1. Additionally, the FTIR for
165
GO sheet also shows the presence of absorption band peaks for hydroxyl, carbonyl, ether and
166
carboxyl groups at 3360.6, 1715.2, 1398 & 1251.9 and 1026.8 & 946.1 cm−1, respectively.
167
rGO: On the other hand, for rGO, the FTIR absorption spectrum (Fig 2c) shows a characteristic
168
sp2 hybridised carbon peak for at 1655.6 cm-1. Moreover, a significant decrease in the intensity
169
of absorption bands peaks corresponding to oxygen functional groups (at 3252.7 cm-1 due to –
170
OH stretching 1395.6 cm-1 due to C–O stretching, and 1034.8 cm−1 due to C–O stretching)
171
confirming the photo-catalytic reduction of GO using NMP. Thus, after the reduction to rGO,
172
the functional groups containing oxygen are removed. The results for FTIR spectra of GO and
173
rGO are in line with Mahesh et al. (Mahesh et al., 2017) ZrGO: The FTIR spectra of ZrGO
174
(Fig 2d) shows a peak at 1038.8 cm-1 which corresponds to Si(Al)O4/2 tetrahedra. The peak at
175
1376.3 cm-1 and 1637.1 cm-1 corresponds to C–O stretching and sp2 hybridised carbon peak
176
respectively. Thus, ZrGO shows characteristic peaks of both zeolite and rGO.
177 178
Fig 2: FTIR absorption spectra for (a) zeolite (b) GO (c) rGO (d) ZrGO. 8
ACCEPTED MANUSCRIPT 179
3.1.2
RAMAN
180
To understand the evolution of rGO, ZrGO from GO, Raman studies have been carried out for
181
GO, rGO and ZrGO. Raman spectra, in Fig 3, show two peaks around 1345 and 1590 cm−1,
182
corresponding to first order D and G bands, respectively. The G band peak corresponds to E2g
183
symmetry of sp2 hybridised carbon atoms, while the D band corresponds to the breathing mode
184
of sp2 hybridised carbon atoms in the hexagonal ring along with the local defects and disorder
185
(Mahesh et al., 2017). The intensity ratio of the D and G bands (ID/IG) is an important and major
186
factor to distinguish GO, rGO and ZrGO composite for structural defects/disorders (Sun et al.,
187
2013). The enhancement of (ID/IG) from ~ 0.99 (GO) to 1.16 (rGO) confirms the reduction of
188
GO (Mahesh et al., 2017) and further enhancement of (ID/IG) to 1.26 confirms the formation
189
of ZrGO as addition of zeolite increases the defects in rGO structure.
190
Fig 3: RAMAN spectra of GO, rGO and ZrGO.
191 192
3.1.3
SEM-EDAX
193
To understand the morphology and elemental composition SEM-EDAX of Zeolite, GO, rGO
194
and ZrGO was performed. Zeolite: Irregular crystals in the SEM micrograph (Fig 4a) indicate
195
towards the formation of zeolite (Musyoka et al., 2013). Zeolites are basically aluminosilicates
196
and it is indicated by the presence of Si and Al content in EDAX (Fig 4b). Other elements 9
ACCEPTED MANUSCRIPT 197
present in the fly ash are sodium, magnesium, calcium, potassium and iron. GO: Morphology
198
of GO is observed as flaky texture reflecting its layered microstructure as shown in SEM image
199
(Fig 4c). Elemental composition (Fig 4d) also supports the formation of GO as it shows
200
presence of carbon and oxygen. rGO: The morphology of rGO (Fig 4e) is observed as layered
201
structure in form of multiple stacked sheets. It can be differentiated from GO by its elemental
202
composition (Fig 4f), nitrogen content in the EDAX is due to the reducing agent (NMP). Also,
203
the reduction of GO is evident by decrease in oxygen percentage. ZrGO: After GO was added,
204
the prepared ZrGO showed the structure of spherical particles (Fig 4g), which may be due to
205
the self-assembly between zeolite and rGO (Vander Waals and hydrogen bonding forces). SEM
206
images show that zeolite particles are decorated over rGO sheets and is indicative of successful
207
formation of the desired composite. Moreover, EDAX of ZrGO (Fig 4h) shows addition of
208
carbon, nitrogen and oxygen apart from the elements present in zeolite, thus indicating towards
209
successful formation of the composite.
10
ACCEPTED MANUSCRIPT
210 211
Fig 4: (a) SEM micrograph of zeolite and (b) elemental composition of zeolite (c) SEM
212
micrograph of GO (d) elemental composition of GO (e) SEM micrograph of rGO (f) elemental
213
composition of rGO (g) SEM micrograph of ZrGO and (b) elemental composition of ZrGO.
214
3.2 Preliminary investigations on synthesized zeolite
215
Preliminary investigations were carried out on prepared zeolite to fix the initial pH and
216
adsorbent dose for further experimentation and comparison purposes. The effect of pH on
217
arsenic adsorption by zeolite was investigated at acidic, neutral, and basic conditions. The pH 11
ACCEPTED MANUSCRIPT 218
of five 50 mL solutions of 100 µg/L arsenic was adjusted to values ranging from 2.0 to 10.0 by
219
adding 0.1MHCl or 0.1MNaOH. The solutions were then mixed with 100 mg of prepared
220
zeolite and stirred for 30 min. After 30 min, samples were removed from the beaker, filtered
221
(0.45 µm nylon membrane filter) and analysed for arsenic concentration. It can be clearly
222
observed (Fig 5a) that with the increase in basicity of the solution the residual arsenic decreases
223
and attains a minimum at pH 8. After which as the pH value is increased from 8 to 10, arsenic
224
concentration also increases slightly. This suggests that for the present study a pH value of 8 is
225
considered to be suitable. Several researchers like Suzuki et al. (Suzuki et al., 2000) and
226
Lenoble et al. (Lenoble et al., 2005) have also found that pH close to 8 has been found suitable
227
for arsenic (III) removal. As the pH increases, amount of negatively charged species of arsenic
228
increases and positively charged species decreases (Altundoğan et al., 2000) and for effective
229
treatment of arsenic (III), the pH of solution must be over 7.0 (Katsoyiannis and Zouboulis,
230
2002).
231 232
Fig 5 Effect of (a) pH (b) dose on residual arsenic concentration when zeolite is used as
233
adsorbent.
234
The effect of zeolite dosage on arsenic adsorption was investigated for five doses 25, 50,
235
75, 100, 125 and 150 mg. The experiments were conducted using 50 ml solution of 100 µg/L
236
arsenic at pH 8 for 30 min. Varying doses of prepared zeolite were mixed with arsenic solution
237
and stirred for 30 min. After 30 min, samples were removed from the beaker, filtered (0.45µm 12
ACCEPTED MANUSCRIPT 238
nylon membrane filter) and analysed for arsenic concentration. The results as obtained are
239
shown in Fig 5b which shows that with increase in zeolite dose the residual arsenic
240
concentration decreases upto the dose of 100 mg adsorbent after which the decrease in arsenic
241
is almost negligible. Therefore, for all the further experiments initial pH was fixed to 8 and
242
adsorbent dose was fixed to 100 µg/L.
243
3.3 Effect of initial arsenic concentration on zeolite, rGO and ZrGO
244
The effect of initial arsenic concentration was studied for zeolite, rGO and ZrGO. The
245
experiments were conducted at a fixed pH of 8 and fixed adsorbent dosage of 100 mg for a
246
duration of 90 min. The samples were collected in an interval of 15 min. It can be observed
247
that at a constant treatment time for all the adsorbents used, an increase in value of initial
248
arsenic concentration also increases value of the residual arsenic concentration. At lower
249
arsenic concentrations, most of the arsenic ions present in the solution would interact with the
250
binding sites facilitating higher adsorption. It can be observed from the Fig 6 that for 100 µg/L
251
initial arsenic concentration and 45 min of treatment time the residual arsenic concentration for
252
zeolite was 24.19 µg/L, for rGO was 19.56 µg/L, and for ZrGO was 8.23 µg/L. Thus, it shows
253
that ZrGO is a better adsorbent for arsenic removal (̴ 93% removal in 45 min) when compared
254
with zeolite and rGO. ZrGO was able to bring down the arsenic concentration well within the
255
WHO permissible limits (<10 µg/L). It can also be observed from the Fig 6a and 6c that at a
256
fixed time of 90 min the residual arsenic increases from 1.52 to 8.19 µg/L as the initial arsenic
257
concentration is increased from 100 to 300 µg/L. It is because at lower concentrations, most of
258
the arsenic ions present in solution would interact with the binding sites facilitating higher
259
adsorption (Chutia et al., 2009).
13
ACCEPTED MANUSCRIPT
260 261
Fig 6: Effect of varying initial arsenic concentration on residual arsenic concentration using
262
zeolite, rGO and ZrGO (a) initial arsenic = 300 µg/L (b) initial arsenic = 200 µg/L (c) initial
263
arsenic = 100 µg/L.
264
For further analysis of results, a graph (Fig 7) was also plotted for ZrGO between time
265
and adsorption capacity (q). It was observed that adsorption capacity increases from 49.24 μg/g
266
to 145.91 μg/g when initial arsenic concentration is increased from 100 to 300 μg/L. This
267
indicates that with the increase of the concentration of arsenic ions in solution, more ions are
268
readily available for adsorption hence increasing the adsorption performance. At higher
269
concentrations, some energetically less favourable sites become involved (Baskan and Pala,
270
2011). However, the sorption is reached to saturated point when the limited active surface sites
271
on the sorbents are covered fully by the sorbate. The present findings of adsorption capacity at
272
100 μg/L initial arsenic (III) concentration was 49.24 μg/g, which was found to be higher than
273
the
274
(Thirunavukkarasu et al., 2003), Iron oxide coated sand (28 µg/g) (Gupta et al., 2005), zeolite
275
(17 µg/g) (Elizalde-González et al., 2001), Oak bark char (7.4 µg/g) (Mohan et al., 2007).
previously
reported
adsorbents
like
granular
ferric
hydroxide
(47.5
µg/g)
276
The arsenic adsorption on zeolites is the result of exchange between terminal aluminol
277
or silanol hydroxyl groups and adsorbate anionic species. The adsorption mechanisms of
278
arsenic anions onto graphene-based materials are complex, the most dominant mechanisms
279
reported in the literature are physical adsorption, chemical interaction and electrostatic
280
attraction (Yang et al., 2017). The mechanism of As (III) adsorption on rGO based composites
14
ACCEPTED MANUSCRIPT 281
should be interpreted as surface complexation modeling. The surface complexation reaction
282
between As(III) and graphene based composites are proposed by Yang et al (Yang et al., 2017).
283
For further information on possible schematic illustration, see Sinha & Shukla (Data in brief;
284
submitted)
285
286 287
Fig 7: Arsenic adsorption by ZrGO as a function of time for varying initial arsenic
288
concentration.
289
4. Adsorption kinetics and adsorption isotherms
290
ZrGO gave the best result as an adsorbent in the present study and was able to bring down the
291
residual arsenic concentration well within the WHO standards. Therefore, the adsorption
292
kinetic and adsorption isotherm study was performed for the data obtained for ZrGO.
293
For the present study, the plots were made for three initial arsenic concentrations (100, 200,
294
300 µg/L). The experimental data was fitted in the mentioned three kinetic models. The average
295
R2 value for pseudo first order kinetic model is 0.976, for pseudo second order kinetic model
296
it is 0.999 and for intra-particle diffusion it is 0.893 The detailed results of adsorption kinetics
297
are presented in Sinha & Shukla (Data in brief; submitted). These results indicate that the
298
adsorption system belongs to the pseudo second-order kinetic model. Similar results have been 15
ACCEPTED MANUSCRIPT 299
obtained by Khatamian et al.(Khatamian et al., 2015). In this model, the rate-limiting step is
300
the surface adsorption that involves chemisorption, where the removal from a solution is due
301
to physicochemical interactions between the two phases (Wang et al., 2007). Liu et al. (Liu et
302
al., 2011) has also mentioned that pseudo-second order kinetic assumes that chemisorption
303
controls the adsorption rate.
304
The experimental data were fitted with Langmuir, Freundlich and Redlich–Peterson isotherms.
305
The R2 values of Redlich–Peterson is the best, 0.986. Thus, it can be concluded that adsorption
306
of arsenic to ZrGO is hybrid mechanism and does not follow ideal monolayer adsorption. For
307
further information on adsorption isotherm analysis see Sinha & Shukla (Data in brief;
308
submitted).
309
5. Conclusions
310
ZrGO composite was successfully synthesized by a simple cost-effective method and can be
311
used as an effective adsorbent for arsenic removal in aqueous solutions. Results showed that
312
ZrGO gave the best performance as an adsorbent to remove arsenic when compared with
313
zeolite and rGO individually. ZrGO shows 97% removal efficiency and was able to bring down
314
the arsenic concentration well within WHO limits. The kinetic model fits the pseudo first order
315
kinetics and indicates the adsorption mechanism to be chemisorption. Adsorption isotherm
316
suitably described by Redlich Peterson isotherm model indicates that the reaction between
317
ZrGO and arsenic in solution is a hybrid mechanism and not an ideal monolayer adsorption.
318
The effective performance of synthesized ZrGO in arsenic removal from water should be
319
amenable to potential water treatment applications in consideration of ZrGO’s low-cost, use of
320
waste material, and favourable adsorption process.
321
Acknowledgements
16
ACCEPTED MANUSCRIPT 322
This work was financially supported by Science and Engineering Board (SERB) project no.
323
PDF/2016/000338 and DST Fast track project no SR/FTP/ES-6/2013.
324
References
325
Altundoğan, H.S., Altundoğan, S., TuÈmen, F., Bildik, M., 2000. Arsenic removal from
326
aqueous solutions by adsorption on red mud. Waste Management 20, 761-767.
327
Baskan, M.B., Pala, A., 2011. Removal of arsenic from drinking water using modified natural
328
zeolite. Desalination 281, 396-403.
329
Benner, S., 2010. Hydrology: anthropogenic arsenic. Nature Geoscience 3, 5-6.
330
Camacho, L.M., Parra, R.R., Deng, S., 2011. Arsenic removal from groundwater by MnO 2-
331
modified natural clinoptilolite zeolite: effects of pH and initial feed concentration. Journal of
332
hazardous materials 189, 286-293.
333
Chunfeng, W., Jiansheng, L., Xia, S., Lianjun, W., Xiuyun, S., 2009. Evaluation of zeolites
334
synthesized from fly ash as potential adsorbents for wastewater containing heavy metals.
335
Journal of Environmental Sciences 21, 127-136.
336
Chutia, P., Kato, S., Kojima, T., Satokawa, S., 2009. Arsenic adsorption from aqueous solution
337
on synthetic zeolites. Journal of Hazardous Materials 162, 440-447.
338
Dubey, C.S., Mishra, B.K., Shukla, D.P., Singh, R.P., Tajbakhsh, M., Sakhare, P., 2012.
339
Anthropogenic arsenic menace in Delhi Yamuna flood plains. Environmental Earth Sciences
340
65, 131-139.
341
El Nemr, A., 2009. Potential of pomegranate husk carbon for Cr (VI) removal from wastewater:
342
Kinetic and isotherm studies. Journal of Hazardous Materials 161, 132-141.
343
Elizalde-González, M., Mattusch, J., Einicke, W.-D., Wennrich, R., 2001. Sorption on natural
344
solids for arsenic removal. Chemical Engineering Journal 81, 187-195.
345
Foo, K., Hameed, B., 2010. Insights into the modeling of adsorption isotherm systems.
346
Chemical Engineering Journal 156, 2-10. 17
ACCEPTED MANUSCRIPT 347
Gimbert, F., Morin-Crini, N., Renault, F., Badot, P.-M., Crini, G., 2008. Adsorption isotherm
348
models for dye removal by cationized starch-based material in a single component system:
349
error analysis. Journal of Hazardous Materials 157, 34-46.
350
Gupta, V., Saini, V., Jain, N., 2005. Adsorption of As (III) from aqueous solutions by iron
351
oxide-coated sand. Journal of colloid and interface science 288, 55-60.
352
Ho, Y., Porter, J., McKay, G., 2002. Equilibrium isotherm studies for the sorption of divalent
353
metal ions onto peat: copper, nickel and lead single component systems. Water, Air, and Soil
354
Pollution 141, 1-33.
355
Hossain, M., Ngo, H., Guo, W., 2013. Introductory of Microsoft Excel SOLVER function-
356
spreadsheet method for isotherm and kinetics modelling of metals biosorption in water and
357
wastewater. Journal of Water Sustainability.
358
Hossain, M., Ngo, H., Guo, W., Setiadi, T., 2012. Adsorption and desorption of copper (II)
359
ions onto garden grass. Bioresource technology 121, 386-395.
360
Kabir, F., Chowdhury, S., 2017. Arsenic removal methods for drinking water in the developing
361
countries: technological developments and research needs. Environmental Science and
362
Pollution Research 24, 24102-24120.
363
Katsoyiannis, I.A., Zouboulis, A.I., 2002. Removal of arsenic from contaminated water sources
364
by sorption onto iron-oxide-coated polymeric materials. Water research 36, 5141-5155.
365
Khatamian, M., Khodakarampoor, N., Oskoui, M.S., Kazemian, N., 2015. Synthesis and
366
characterization of RGO/zeolite composites for the removal of arsenic from contaminated
367
water. RSC Advances 5, 35352-35360.
368
Kumar, K.V., 2007. Optimum sorption isotherm by linear and non-linear methods for malachite
369
green onto lemon peel. Dyes and Pigments 74, 595-597.
370
Kumar, P.R., Chaudhari, S., Khilar, K.C., Mahajan, S., 2004. Removal of arsenic from water
371
by electrocoagulation. Chemosphere 55, 1245-1252.
18
ACCEPTED MANUSCRIPT 372
Langmuir, I., 1916. The constitution and fundamental properties of solids and liquids. Part I.
373
Solids. Journal of the American chemical society 38, 2221-2295.
374
Lenoble, V., Laclautre, C., Deluchat, V., Serpaud, B., Bollinger, J.-C., 2005. Arsenic removal
375
by adsorption on iron (III) phosphate. Journal of hazardous materials 123, 262-268.
376
Li, Z., Wang, L., Meng, J., Liu, X., Xu, J., Wang, F., Brookes, P., 2018. Zeolite-supported
377
nanoscale zero-valent iron: New findings on simultaneous adsorption of Cd (II), Pb (II), and
378
As (III) in aqueous solution and soil. Journal of hazardous materials 344, 1-11.
379
Liu, B., Wang, D., Gao, X., Zhang, L., Xu, Y., Li, Y., 2011. Removal of arsenic from Laminaria
380
japonica Aresch juice using As (III)-imprinted chitosan resin. European Food Research and
381
Technology 232, 911.
382
Luo, Y.-B., Cheng, J.-S., Ma, Q., Feng, Y.-Q., Li, J.-H., 2011. Graphene-polymer composite:
383
extraction of polycyclic aromatic hydrocarbons from water samples by stir rod sorptive
384
extraction. Analytical Methods 3, 92-98.
385
Mahesh, S., Pawan, K., Rudra, K., Satinder Kumar, S., Ajay, S., 2017. Photo-catalytic
386
reduction of oxygenated graphene dispersions for supercapacitor applications. Journal of
387
Physics D: Applied Physics 50, 124003.
388
Merrikhpour, H., Jalali, M., 2013. Comparative and competitive adsorption of cadmium,
389
copper, nickel, and lead ions by Iranian natural zeolite. Clean Technologies and Environmental
390
Policy 15, 303-316.
391
Mohan, D., Pittman, C.U., 2007. Arsenic removal from water/wastewater using adsorbents—
392
a critical review. Journal of Hazardous materials 142, 1-53.
393
Mohan, D., Pittman, C.U., Bricka, M., Smith, F., Yancey, B., Mohammad, J., Steele, P.H.,
394
Alexandre-Franco, M.F., Gómez-Serrano, V., Gong, H., 2007. Sorption of arsenic, cadmium,
395
and lead by chars produced from fast pyrolysis of wood and bark during bio-oil production.
396
Journal of colloid and interface science 310, 57-73.
19
ACCEPTED MANUSCRIPT 397
Mondal, P., Bhowmick, S., Chatterjee, D., Figoli, A., Van der Bruggen, B., 2013. Remediation
398
of inorganic arsenic in groundwater for safe water supply: a critical assessment of technological
399
solutions. Chemosphere 92, 157-170.
400
Musyoka, N.M., Petrik, L.F., Fatoba, O.O., Hums, E., 2013. Synthesis of zeolites from coal fly
401
ash using mine waters. Minerals Engineering 53, 9-15.
402
Ng, J., Cheung, W., McKay, G., 2002. Equilibrium studies of the sorption of Cu (II) ions onto
403
chitosan. Journal of Colloid and Interface Science 255, 64-74.
404
Nidheesh, P., Singh, T.A., 2017. Arsenic removal by electrocoagulation process: Recent trends
405
and removal mechanism. Chemosphere 181, 418-432.
406
Ojha, K., Pradhan, N.C., Samanta, A.N., 2004. Zeolite from fly ash: synthesis and
407
characterization. Bulletin of Materials Science 27, 555-564.
408
Polowczyk, I., Bastrzyk, A., Ulatowska, J., Szczałba, E., Koźlecki, T., Sadowski, Z., 2016.
409
Influence of pH on arsenic (III) removal by fly ash. Separation Science and Technology 51,
410
2612-2619.
411
Querol, X., Alastuey, A., Moreno, N., Alvarez-Ayuso, E., Garcı́a-Sánchez, A., Cama, J.,
412
Ayora, C., Simón, M., 2006. Immobilization of heavy metals in polluted soils by the addition
413
of zeolitic material synthesized from coal fly ash. Chemosphere 62, 171-180.
414
Redlich, O., Peterson, D.L., 1959. A useful adsorption isotherm. Journal of Physical Chemistry
415
63, 1024-1024.
416
Shevade, S., Ford, R.G., 2004. Use of synthetic zeolites for arsenate removal from pollutant
417
water. Water Research 38, 3197-3204.
418
Shukla, D.P., Dubey, C., Singh, N.P., Tajbakhsh, M., Chaudhry, M., 2010. Sources and
419
controls of Arsenic contamination in groundwater of Rajnandgaon and Kanker District,
420
Chattisgarh Central India. Journal of hydrology 395, 49-66.
20
ACCEPTED MANUSCRIPT 421
Simeonidis, K., Mourdikoudis, S., Kaprara, E., Mitrakas, M., Polavarapu, L., 2016. Inorganic
422
engineered nanoparticles in drinking water treatment: a critical review. Environmental Science:
423
Water Research & Technology 2, 43-70.
424
Sinha, R., Mathur, S., 2016. Control of aluminium in treated water after defluoridation by
425
electrocoagulation and modelling of adsorption isotherms. Desalination and Water Treatment
426
57, 13760-13769.
427
Soni, M., Arora, T., Khosla, R., Kumar, P., Soni, A., Sharma, S.K., 2016. Integration of Highly
428
Sensitive Oxygenated Graphene With Aluminum Micro-Interdigitated Electrode Array Based
429
Molecular Sensor for Detection of Aqueous Fluoride Anions. IEEE Sensors Journal 16, 1524-
430
1531.
431
Soni, M., Kumar, P., Pandey, J., Sharma, S.K., Soni, A., 2018. Scalable and site specific
432
functionalization of reduced graphene oxide for circuit elements and flexible electronics.
433
Carbon 128, 172-178.
434
Sun, H., Wang, Y., Liu, S., Ge, L., Wang, L., Zhu, Z., Wang, S., 2013. Facile synthesis of
435
nitrogen doped reduced graphene oxide as a superior metal-free catalyst for oxidation.
436
Chemical Communications 49, 9914-9916.
437
Suzuki, T.M., Bomani, J.O., Matsunaga, H., Yokoyama, T., 2000. Preparation of porous resin
438
loaded with crystalline hydrous zirconium oxide and its application to the removal of arsenic.
439
Reactive and functional Polymers 43, 165-172.
440
Tavolaro, A., Drioli, E., 1999. Zeolite membranes. Advanced materials 11, 975-996.
441
Thirunavukkarasu, O., Viraraghavan, T., Subramanian, K., 2003. Arsenic removal from
442
drinking water using granular ferric hydroxide. Water Sa 29, 161-170.
443
Vanderborght, B.M., Van Grieken, R.E., 1977. Enrichment of trace metals in water by
444
adsorption on activated carbon. Analytical chemistry 49, 311-316.
21
ACCEPTED MANUSCRIPT 445
Wang, H., Yuan, X., Wu, Y., Huang, H., Peng, X., Zeng, G., Zhong, H., Liang, J., Ren, M.,
446
2013a. Graphene-based materials: fabrication, characterization and application for the
447
decontamination of wastewater and wastegas and hydrogen storage/generation. Advances in
448
colloid and interface science 195, 19-40.
449
Wang, H., Zhou, A., Peng, F., Yu, H., Yang, J., 2007. Mechanism study on adsorption of
450
acidified multiwalled carbon nanotubes to Pb (II). Journal of Colloid and Interface Science
451
316, 277-283.
452
Wang, S., Sun, H., Ang, H.-M., Tadé, M., 2013b. Adsorptive remediation of environmental
453
pollutants using novel graphene-based nanomaterials. Chemical Engineering Journal 226, 336-
454
347.
455
Wdowin, M., Franus, M., Panek, R., Badura, L., Franus, W., 2014. The conversion technology
456
of fly ash into zeolites. Clean Technologies and Environmental Policy 16, 1217-1223.
457
Wu, L.-K., Wu, H., Liu, Z.-Z., Cao, H.-Z., Hou, G.-Y., Tang, Y.-P., Zheng, G.-Q., 2017. Highly
458
porous copper ferrite foam: A promising adsorbent for efficient removal of As (III) and As (V)
459
from water. Journal of Hazardous Materials.
460
Yang, X., Xia, L., Song, S., 2017. Arsenic adsorption from water using graphene-based
461
materials as adsorbents: a critical review. Surface Review and Letters 24, 1730001.
462
Yusuf, M., Elfghi, F., Zaidi, S.A., Abdullah, E., Khan, M.A., 2015. Applications of graphene
463
and its derivatives as an adsorbent for heavy metal and dye removal: a systematic and
464
comprehensive overview. RSC Advances 5, 50392-50420.
465
Zhu, J., Wang, Y., Liu, J., Zhang, Y., 2014. Facile one-pot synthesis of novel spherical zeolite–
466
reduced graphene oxide composites for cationic dye adsorption. Industrial & Engineering
467
Chemistry Research 53, 13711-13717.
468
22
ACCEPTED MANUSCRIPT Highlights
Fly ash based ZrGO was successfully synthesized by a simple and cost-effective process.
ZrGO was able to reduce the arsenic concentration within WHO permissible limit.
ZrGO shows 97% removal efficiency.
Adsorption capacity of ZrGO was 49.23-145.91 µg/g.